Device for preventing intrusion of foreign matter into dental handpiece

Claim 1

In a dental handpiece comprising in combination a rotatable bur sleeve for rotatably receiving and securing a dental tool introduced through a tool inserting opening and a bearing for rotatably supporting said bur sleeve with respect to a stationary main body of the handpiece, an improvement wherein said handpiece comprises in combination a device for preventing intrusion of foreign matter into inside of the handpiece, including: a rotatable member secured to said bur sleeve for rotation in unison with said bur sleeve, a gap section formed on an outer periphery of said rotatable member for communicating at one end thereof with said bearing and opening at the other end thereof at a distal end of said handpiece, and a discharge port formed in the vicinity of the distal end of the entail handpiece, said discharge port passing through said main body of the handpiece and communicating with said gap section, wherein a stationary partitioning member secured to said main body of the handpiece is provided on an outer periphery of said bur sleeve for delimiting a first gap section communicating with said bearing, said gap section includes said first gap section, a second gap section delimited between an outer periphery of said stationary partitioning member and an inner periphery of said rotatable member, and communicating with said first gap section, and a third gap section formed on the outer periphery of said rotatable member, said third gap section communicating at one end thereof with said second gap section and opening in the vicinity of the distal end of the dental handpiece, wherein, with rotation of said bur sleeve, air pressure within said gap sections is decreased in sequence of said first gap section, said second gap section and said third gap section, and whereby the foreign matter including cut tooth particles is sucked into said gap sections so as to be expelled to outside on the main body of the handpiece through said discharge port under centrifugal force induced by rotation of said rotatable member.